MESOSCALE DISCUSSION 0035
   NWS STORM PREDICTION CENTER NORMAN OK
   1002 PM CST FRI JAN 20 2012
   
   AREAS AFFECTED...ERN AR...NRN MS...SRN TN...NW AL
   
   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 
   
   VALID 210402Z - 210530Z
   
   A SEVERE THREAT IS EXPECTED TO DEVELOP ACROSS ERN AR...NRN MS...SRN
   TN AND NW AL LATE THIS EVENING OR EARLY DURING THE OVERNIGHT PERIOD.
   AN ISOLATED THREAT FOR TORNADOES AND WIND DAMAGE MAY EXIST AS STORMS
   INCREASE IN COVERAGE OVER THE NEXT 2 TO 4 HOURS. WW ISSUANCE MAY
   BECOME NECESSARY ACROSS THE REGION.
   
   THE LATEST SFC ANALYSIS SHOWS A 1007 MB LOW NEAR TEXARKANA WITH A
   STATIONARY FRONT EXTENDING ENEWD FROM THE LOW ACROSS ERN AR INTO
   SWRN TN AND NRN AL. THUNDERSTORMS ARE DEVELOPING IN NW TN ON THE NRN
   SIDE OF THE FRONTAL BOUNDARY AHEAD OF A VORTICITY MAX AND SHORTWAVE
   TROUGH LOCATED IN CNTRL MO. AS THIS FEATURE MOVES EWD...LARGE-SCALE
   ASCENT WILL INCREASE IN THE TN VALLEY HELPING TO INITIATE STORMS
   ALONG THE FRONT. THIS ACTIVITY SHOULD INCREASE QUICKLY IN THE 06Z TO
   09Z TIMEFRAME WITH STORMS LIKELY MOVING ENEWD ACROSS THE MCD AREA.
   MESOSCALE ANALYSIS ALONG AND JUST SOUTH OF THE BOUNDARY SUGGEST
   MLCAPE VALUES ARE IN THE 500 TO 1000 J/KG RANGE. THIS COMBINED WITH
   THE LACK OF A STRONG INVERSION LAYER SOUTH OF THE BOUNDARY SHOULD
   ALLOW FOR SFC-BASED THUNDERSTORM DEVELOPMENT. FORECAST SOUNDINGS
   TONIGHT SOUTH OF MEMPHIS AND NEAR TUPELO SHOW 45 TO 55 KT OF DEEP
   LAYER SHEAR ALONG WITH UNIDIRECTIONAL WIND PROFILES. THIS WOULD
   FAVOR A WIND DAMAGE THREAT IF CELLS CAN ORGANIZE INTO A LINE. IF THE
   CELLS TEND TO REMAIN DISCRETE AND ROTATE...THEN THE STRONG SPEED
   SHEAR IN THE BOUNDARY LAYER MAY ALLOW AN ISOLATED TORNADO THREAT TO
   DEVELOP.
   
   ..BROYLES.. 01/21/2012
   
   
   ATTN...WFO...OHX...HUN...MEG...JAN...LZK...
   
   LAT...LON   34428793 34638718 34958641 35218629 35478641 35688678
               35818739 35708875 35119042 34759090 34329109 34009105
               33729076 33739001 33998906 34428793